Many battery powered wireless devices have a sleep, or idle, mode in which they are able to conserve power by powering down components such as their receivers. In the sleep mode, a communication unit is not on a traffic channel and it conserves power by periodically checking for incoming messages. These communication units then periodically “wake up” to determine if any page messages (pages) are being selectively transmitted to them. If there are no pages that the wireless device determines are destined for reception by the wireless device, it will power down in order to conserve power and extend its battery life. For example, Code-Division Multiple-Access (CDMA) cellular communication systems, more commonly referred to as CDMA 2000, 3GPP2 UMB (Ultra Mobile Broadband), or Wideband CDMA systems, also known as Universal Mobile Telecommunication System (UMTS), incorporate such power saving techniques. Each wireless device within a CDMA 2000 system is normally able to determine to which group of four, 20 millisecond (ms), synchronous frames on its paging channel (PCH) it is assigned. This group of frames, referred to as its “paging slot,” is used by the infrastructure to transmit page messages to the particular unit. In other technologies, this is referred to as a superframe, and a first super frame conveys the QPC, an immediately subsequent super frame conveys the corresponding paging message. This configuration of the transmission of the QPC message followed by the page message is also referred to as a short paging gap or short gap. Thus, a communication unit in so-called “slotted mode” operation periodically exits its sleep mode in order to monitor transmissions associated with its assigned paging slot. The faster a communication unit can determine that it has no page message to receive, the faster it can return to sleep mode and conserve power, further extending its battery life.
In certain communication systems, such as CDMA 2000 & 3GPP2 UMB (Ultra Mobile Broadband), a Quick Paging Channel (QPCH) is incorporated to reduce the time a communication unit monitors the PCH slot for a page message. A QPC message is transmitted in the QPCH earlier than the corresponding page message transmitted in the PCH slot. Certain paging indicator bits are transmitted in the QPC message that tell each wireless device whether it is being selected for reception of a page message. Either the QPC message specifically selects the wireless device or it indicates that the wireless device may be selected by a subsequent page message transmitted in the PCH slot. Because the QPC message does not employ error correction coding or interleaving as does the page message transmitted in the PCH slot, the time required for a wireless device to receive and process its QPC message is small compared to the time required to monitor the longer page message in the PCH slot. Thus, the QPC message allows wireless devices to determine whether they need to monitor the upcoming corresponding page message transmitted in the PCH slot at all. Normally, a large number of wireless devices determine, based on the QPC message, that they do not need to monitor for the page message in the upcoming corresponding PCH slot and they can rapidly/immediately re-enter a “sleep mode,” where battery power is conserved and battery life is extended.
The use of QPC message followed by a corresponding page message is an example of a two phase paging system that is included in certain wireless communication systems, such as in CDMA 2000, UMTS, and 3GPP2 UMB (Ultra Mobile Broadband), and in communication standards such as LTE 3GPP—(long-term evolution). During the first phase, a shorter more ambiguous message is sent to all wireless devices that are periodically monitoring for their selection by a transmitted page message. The purpose of this shorter and typically more ambiguous message (also known as a QPC message) is to quickly inform a large fraction of wireless devices that they are not the intended recipient of the page message. The remaining wireless device(s), which during the first phase is/are not sure if they are being paged, additionally monitor the information received in the second phase of the paging message. Based on the information in the second phase of the paging message, each of the remaining wireless device(s) can determine if it is being paged. The second phase of the paging message is not ambiguous. At this point, all wireless devices that are not being paged should be able to go to sleep. Wireless device that is being paged typically responds (such as by transmitting a handshake message back to the system) or performs a function dependent on the received QPC message or page message. Throughout this application, when the term QPC message is used, it is used to generally refer to the first phase of a two-phased page in any such two-phased paging system. When the term page message or PCH slot is mentioned, it is referring to the second phase of a two-phased page in any such two-phased paging system.
The time delay between the QPC message and the corresponding page message is known as the paging gap time or gap time. This gap time is a fixed time delay for all wireless devices in a communication system.
The delay time is set to allow wireless devices to conserve power by idle (power down) waiting for the time to monitor for the subsequent page message and while at the same time it allows a wireless device that determines from the QPC message that it is being selected for a page to quickly respond by, for example, transmitting a handshake message back to the system. In such a case, the system can avoid transmitting the subsequent page message because the system knows that the selected wireless device has already responded to the QPC message. Therefore, the time where the subsequent message would have been transmitted can be better used by the system to transmit other information to the wireless devices. This helps improve system capacity for more communications over the limited resource of the wireless communication channel.
Regrettably, using a fixed time delay for the gap time for all wireless devices in a communication system can result in a poor compromise that can detrimentally affect battery life for a large number of wireless devices in the system. Some wireless devices may need to have a short gap time and a short paging cycle, for example, repeatedly monitoring the wireless communication channel for page messages many times a second, because they need to respond quickly to a transmitted page. Other wireless devices that are not as time sensitive to responding to a transmitted page could have a much longer paging cycle, such as every five seconds. These wireless devices also could benefit from a longer gap time to conserve battery power while allowing one of these wireless devices to transmit the handshake message back to the system. Because all wireless devices will have to use the same short gap time that is fixed for all wireless devices in the wireless communication system, this timing constraint may result in a wireless device transmitting a handshake message back to the system after the end of the gap time. Therefore, it leaves no time for the system to avoid sending the subsequent page message resulting in wasted transmissions of the second page message. This reduces system communication efficiency and capacity.
Therefore a need exists to overcome the problems with the prior art as discussed above.